“Our study demonstrates the high sensitivity of [gallium Ga-68 dotatate] in the localization of [ectopic Cushing’s syndrome], for both occult primary tumors and metastatic lesions,” the researchers wrote. “Importantly, the use of [gallium Ga-68 dotatate] impacted clinical management in 64% of patients with [ectopic Cushing’s syndrome] overall.” The researche […]

The 11th annual Pituitary Day will take place on October 19, 2019 Patients living with pituitary disorders can hear lectures from our pituitary specialists, see movies of pituitary surgeries and hear from other patients about their experience living with pituitary disease and undergoing surgery.

Cynthia is from Ruckersville, VA. She is testing for Cushing's due to many symptoms. tested for CD because after exhaustive research on AVN (Avascular Necrosis) related to other diseases. I have four known areas of AVN & after seeing the symptoms of CD, I realized may have this. I also have numerous other diseases Lupus, Sojgrens, Hypothyroid, High […]

Today is the Thirteenth Anniversary of my kidney cancer surgery. These thirteen years have been bonus years for me. For my cancer stage, the 5-year survival rate was 81% and I’ve made it more than twice that long – so far.

Kathy was diagnosed with a pituitary tumor in 1991. At the time the only symptom she was aware of was a severe headache. She had a transsphenoidal resection followed by radiation therapy for 23 days. They said they could not remove all of the tumor.

Sadly, we lost another Cushing’s patient on Friday, May 9, 2014. Melinda was a member of the Cushing’s Help message boards since Jun 24, 2007. She was only 25 and left behind a young son and many loving family members.

He died of a presumed heart attack. September 19, 2015 he said "'I was diagnosed hypertensive way back when I was 20. The condition remained for years, and became more acute with my cushings pit tumor. I still have high blood pressure, partially teated with three meds. I'll have to consult my doc and see if this may also be an issue."

'My name is Caroline and I dont post often but have met a few of you guys and read the board regularly, it has definitely been a godsend to cushies everywhere. The reason I am writing tonight is I have just received devastating information about a dear friend of mine, and a woman some of you may have met during testing. Her name is Kathryn Miller and sh […]

Patients with growth hormone deficiency due to nonfunctioning pituitary adenoma experienced excessive morbidity due to cerebral infarction and sepsis regardless of whether they received long-term GH therapy, whereas treatment was associated with a normal incidence of type 2 diabetes, despite higher BMI and more severe hypopituitarism in treated patients, according to findings from an observational, registry-based study.

“Although growth hormone replacement therapy is well-established and reverses most of the features associated with GH [deficiency], one of the safety concerns is the reduction in insulin sensitivity and the potential risk of developing type 2 diabetes mellitus,” Daniel S. Olsson, MSc, MD, PhD, professor at the Sahlgrenska Academy Institute of Medicine at the University of Gothenburg, Sweden, and colleagues wrote in the study background.

Studies examining whether there is an association have produced mixed results, the researchers wrote, and it remains unknown to what extent GH deficiency — and GH therapy —contribute to the development of type 2 diabetes and other comorbidities, including cerebral infarction, malignant tumors, myocardial infarction or fractures.

Olsson and colleagues analyzed data from 426 patients treated or followed for nonfunctioning pituitary adenoma between 1997 and 2011, selected from the Swedish National Patient Register. Researchers assessed information on tumor treatment, hormone therapy, antihypertensive medication, BMI and duration of GH therapy. For patients with type 2 diabetes, researchers assessed HbA1c values, insulin treatment, oral antidiabetes therapies and lipid-lowering therapies. Researchers followed the cohort through December 2014 or until death. Patients were stratified by use of GH therapy. Researchers calculated standardized incidence ratios (SIRs) based on the observed number of comorbidities among patients with nonfunctioning pituitary adenoma vs. the expected number of comorbidities in the background population.

Within the cohort, 207 patients received GH therapy (145 men) and 219 did not (129 men). Median duration of GH therapy was 11.7 years; mean age at diagnosis was 56 years for treated patients and 65 years for untreated patients. Median follow-up time for treated and untreated patients was 12.2 years and 8.2 years, respectively.

Incidence of cerebral infarction was increased for the whole cohort regardless of GH therapy status, with an SIR of 1.39 (95% CI, 1.03-1.84), and was most evident among 97 patients who underwent radiotherapy, in which 19 cerebral infarctions occurred vs. the expected number of 9.8 (P = .011).

“The study showed an increased overall incidence of cerebral infarction in patients with [nonfunctioning pituitary adenoma] compared to the general population that was related to previous radiotherapy, but not to GH [replacement therapy],” the researchers wrote.

Incidence of myocardial infarction was similar for treated and untreated patients, with SIRs of 1.18 (95% CI, 0.73-1.8) and 1.23 (95% CI, 0.82-1.78), respectively. Incidence of receiving medical treatment for hypertension was also similar between groups.

In assessing incidence of type 2 diabetes, the researchers found that the SIR was higher among untreated patients (1.65; 95% CI, 1.06-2.46) vs. treated patients, who had an SIR similar to the background population (0.99; 95% CI, 0.55-1.63). Treated patients with type 2 diabetes had higher BMI vs. untreated patients with type 2 diabetes (P = .01), according to researchers, and glycemic status was similar among treated and untreated patients.

The incidence of sepsis requiring hospitalization was also similar between treated and untreated patients, with rates for both groups close to double that of the background population (P < .001). Incidence of malignant tumors was not increased for treated or untreated patients when compared against the background population, according to the researchers. – by Regina Schaffer

Disclosures: The Gothenburg Growth Hormone Database is supported partly through unrestricted grants from Novo Nordisk, Pfizer and Sandoz. Olsson reports he has served as a consultant for Ipsen, Pfizer and Sandoz. Another author reports he has served as a consultant to AstraZeneca and Viropharma/Shire, and received lecture fees from Novo Nordisk, Otsuka and Pfizer.

Rare in children and adolescents, Cushing’s disease refers to overproduction of cortisol caused by excessive adrenocorticotropic hormone (ACTH) secretion from a pituitary tumor. In pediatrics, early symptoms of excess cortisol include weight gain and delayed growth.

Despite being extremely unlikely in children younger than 7, some cases of Cushing’s disease in infancy have been reported.

“If undiagnosed or untreated it can lead to considerable morbidity and mortality, and the inability to detect a microadenoma [tumors smaller than 10 mm in diameter] on magnetic resonance imaging (MRI) can lead to a diagnostic dilemma leading to unnecessary delays in treatment initiation,” the researchers wrote.

Researchers from the Indraprastha Apollo Hospital in New Delhi, India, described a 7-year-old boy who complained of excessive appetite and weight gain in the previous five months. The child weighed 46.8 kg, was 127 cm tall, and had a body mass index (BMI) of 29, indicating he was overweight.

The child’s excess fat was mainly in his abdomen plus he had a round, red, puffy face, which are both common features of Cushing’s disease. He had no history of acute or chronic steroid intake, mood swings, sleep disorders, or issues with eyesight.

Given his clinical presentation, the investigators suspected the boy had Cushing’s disease or pseudo-Cushing’s disease, which refers to situations where the overproduction of cortisol is caused by something unrelated to the disease, such as stress or uncontrolled diabetes mellitus.

Biochemical testing showed the patient had high levels of cortisol, which remained unchanged after a dexamethasone suppression test. In addition, his levels of “bad” cholesterol, referring to low-density lipoprotein, were extremely elevated at 194 mg/dL, where a normal range is defined as less than 110 mg/dL.

Imaging revealed no lesions in the pituitary gland.

The boy was sent home with dietary recommendations. Eight weeks later, he had lost 4 kg, while his height remained the same; he also complained of headaches and various episodes of double vision.

This confused the clinical team as hallmarks of Cushing’s disease include short stature and weight loss triggered by pharmacological therapy. Despite having lost weight, he did not take any medications to help him with it, plus the boy’s height was normal for his age.

Nonetheless, the patient was complaining of neurological symptoms, suggesting progression of Cushing’s disease.

An ophthalmologist did not observe anything abnormal with the child’s eyes that could explain his double vision episodes.

Magnetic resonance imaging (MRI) showed a small microadenoma in the right lobe of the pituitary gland.

Using Gamma Knife radiation therapy, a kind of high-precision radiation therapy, and surgery, doctors successfully removed the boy’s microadenoma. Six weeks post-procedure, his cortisol and ACTH concentrations returned to normal.

“MRI findings of the pituitary may be inconclusive in the beginning of the disease process and should be borne in mind during further follow-up. In cases where a clear-cut diagnosis may be difficult, a diligent follow-up is required to ascertain the course of the disease and to make timely diagnosis,” the investigators concluded.

Abstract

Objective Cushing’s disease (CD) is a rare endocrine disorder characterized by excess secretion of ACTH due to a pituitary adenoma. Current treatment options are limited and may pose additional risks. A literature review was conducted to assess the holistic burden of CD.

Design Studies published in English were evaluated to address questions regarding the epidemiology of CD, time to diagnosis, health-related quality of life (HRQoL), treatment outcomes, mortality, prevalence of comorbidities at diagnosis, and reversibility of comorbidities following the treatment.

Methods A two-stage literature search was performed in Medline, EMBASE, and Science Citation Index, using keywords related to the epidemiology, treatment, and outcomes of CD: i) articles published from 2000 to 2012 were identified and ii) an additional hand search (all years) was conducted on the basis of bibliography of identified articles.

Results At the time of diagnosis, 58–85% of patients have hypertension, 32–41% are obese, 20–47% have diabetes mellitus, 50–81% have major depression, 31–50% have osteoporosis, and 38–71% have dyslipidemia. Remission rates following transsphenoidal surgery (TSS) are high when performed by expert pituitary surgeons (rates of 65–90%), but the potential for relapse remains (rates of 5–36%). Although some complications can be partially reversed, time to reversal can take years. The HRQoL of patients with CD also remains severely compromised after remission.

Conclusions These findings highlight the significant burden associated with CD. As current treatment options may not fully reverse the burden of chronic hypercortisolism, there is a need for both improved diagnostic tools to reduce the time to diagnosis and effective therapy, particularly a targeted medical therapy.

Although there have been several consensus statements published recently on the definition of remission, diagnosis, and the management of CD, the severity and diversity of the clinical scenario and associated morbidities continue to present a management challenge (1, 22, 23). Additionally, there is recent evidence of persistent deleterious effects after remission, most notably persistent elevated cardiovascular risk (3, 22). The main objective of the current literature review is to describe the current burden of the disease and to summarize data on specific aspects of this burden, which underscores the need for improved diagnostic and therapeutic approaches.

Materials and methods

Available literature were evaluated to address questions regarding the epidemiology of CD, time to diagnosis, mortality, prevalence of comorbidities at diagnosis, reversibility of comorbidities after treatment (in particular, after disease remission), outcomes and complications of current treatment options, and HRQoL associated with CD and interventions.

The literature search was performed in Medline, EMBASE, and Science Citation Index, using keywords related to the epidemiology, treatment, and outcomes of CD. It was conducted in two stages: i) articles published between 2000 and 2012 were identified through a PubMed search using the following keywords: CD, incidence, prevalence, mortality, treatment, remission, cure, excess cortisol, outcomes, cost, QoL, morbidities, transsphenoidal surgery (TSS), adrenalectomy, radiotherapy, steroidogenesis inhibitors, ketoconazole, mitotane, aminoglutethimide, etomidate, metyrapone, pasireotide, and cortisol receptor antagonists; and ii) an additional hand search was conducted on the basis of the bibliographies of identified articles. All studies that provided data (regardless of publication year) related to these research questions were retained.

Definitions

Different criteria for defining the remission of hypercortisolism have been proposed, ranging from the occurrence of definitive or transient postoperative hypocortisolemia to the adequate suppression of cortisol after dexamethasone administration. According to a recent consensus statement (23), persistent postoperative morning serum cortisol levels of <2 μg/dl (∼50 nmol/l) are associated with remission and a low recurrence rate of ∼10% at 10 years. Persistent serum cortisol levels above 5 μg/dl (∼140 nmol/l) for up to 6 weeks following surgery require further evaluation. When serum cortisol levels are between 2 and 5 μg/dl, the patient can be considered in remission and can be observed without additional treatment for CD. A subset of patients can even develop complete adrenal insufficiency (serum cortisol levels below 2 μg/dl (∼50 nmol/l)) up to 12 weeks postsurgery (24, 25). Therefore, repeated evaluation in the early postoperative period is recommended. However, long-term follow-up is necessary for all patients because no single cortisol cutoff value excludes those who later experience disease recurrence, and up to 25% of patients develop a recurrent adenoma within 10 years after surgery (26, 27, 28).

Results

Incidence and prevalence of CD

Although epidemiologic data on CD are limited, several population-based studies indicate an incidence of 1.2–2.4 per million (14, 19) and the prevalence of diagnosed cases to be ∼39 per million population (14). Lindholm et al. (19) used the case definition as either the presence of a corticotroph adenoma or remission after neurosurgery, which yielded an estimated incidence rate of 1.2–1.7 per million per year. Etxabe & Vazquez (14) reported an incidence of 2.4 per million in Vizcaya, Spain. A large-scale retrospective survey carried out in New Zealand by Bolland et al. (29) found the approximate prevalence of all forms of Cushing’s syndrome (CS) (the majority of these cases were of pituitary origin) to be 79 per million and the incidence to be 1.8 per million per year. Differences in epidemiologic estimates may be attributable to varying case definitions (for instance, the study by Lindholm excluded cases in which the adenoma could not be localized or those that could not achieve remission from surgery), geographical differences, and temporal effects. The prevalence of CD may be underestimated due to unrecognized patients with mild symptoms and patients with a cyclic form of CD (30).

Time to diagnosis

Data on the time from onset of symptoms to diagnosis are also limited. In a prospective study by Flitsch et al. (31) of 48 patients with pituitary adenomas, including 19 who had ACTH-secreting adenomas causing CD, the reported time from onset of symptoms to diagnosis was 4.3 years. A study by Martinez Ruiz et al. (32), which was based on only four pediatric CD patients, reported the time between onset of symptoms and diagnosis as ranging from 2.5 to 5 years. Etxabe & Vazquez (14) estimated that the average time from onset of clinical symptoms to diagnosis in 49 CD patients was 45.8±2.7 months (6–144 months), thus 3.8 years. This is corroborated by the findings from a Belgian cross-sectional study on pituitary adenomas including CD, which estimated that patients experienced symptoms for an average of 45 months before diagnosis (33). However, the reliability and generalizability of these data are limited by small sample sizes and the retrospective nature of the studies. Indeed, the New Zealand data from Bolland et al. (29) report that on presentation, patients experienced symptoms for a median of 2.0 years (but ranging up to 20 years) before diagnosis. On the basis of data from the prospective European Registry on Cushing’s syndrome (ERCUSYN) (total number of patients=481, of whom 66% of patients had CD), median delay in diagnosis was 2 years (34).

Mortality in patients with CD

Mortality in patients with CD has been analyzed in several small studies, with overall rates reported as standardized mortality ratio (SMR) ranging from 1.7 to 4.8 (Table 1) (14, 15, 17, 19). In studies in which mortality was assessed among those in remission and those with persistent disease separately, patients with persistent hypercortisolemia consistently had the highest mortality risk (15, 19, 35, 36). In addition, TSS as a first-line treatment has been an important advance as high remission rates after initial surgery have been accompanied by mortality rates that mirror those observed in the general population (17, 35, 37). In a case series from the UK, it was found that the majority of deaths occurred before 1985, which was before TSS was employed as the routine first-line treatment at the center (36). In a recent retrospective study, 80 patients undergoing TSS for CD between 1988 and 2009 were evaluated, and long-term cure (defined as ongoing absence of hypercortisolism at last follow-up) was reported in 72% of patients. However, overall elevated mortality persisted in patients (SMR 3.17 (95% CI: 1.70–5.43)), including those who achieved ‘cure’ (SMR 2.47 (95% CI: 0.80–5.77)), although even higher mortality was seen in those with postoperative recurrence/persistent disease (SMR 4.12 (95% CI: 1.12–10.54) (38). Additionally, a nationwide, retrospective study in New Zealand reported significant persistently increased mortality both in macro- and microadenomas (SMR 3.5 (1.3–7.8) and 3.2 (2.0–4.8) respectively), despite long-term biochemical remission rates of 93 and 91% of patients, respectively (29).

More than a century ago, Harvey Cushing introduced the term “pluriglandular syndrome” to describe a disorder characterized by rapid development of central obesity, arterial hypertension, proximal muscle weakness, diabetes mellitus, oligomenorrhea, hirsutism, thin skin, and ecchymoses.1 Cushing knew that this syndrome was associated with adrenal cancer,2 and he suspected that some cases might have a pituitary component.

On September 6, 1911, he performed a craniotomy on one of his patients (referred to as Case XLV) but found no pituitary tumor.3 In his description of the case, he goes on to say that “we may perchance be on the way toward the recognition of the consequences of hyperadrenalism.”2 With time, it became clear that the disorder could be caused by small basophilic adenomas of the pituitary gland,4 and the pluriglandular syndrome became known as Cushing’s syndrome.

Fuller Albright provided the next conceptual advance in an extraordinary report, published in the first volume of the Laurentian Hormone Conference, “The Effects of Hormones on Osteogenesis in Man”5:

It has been our concept that protoplasm in general, like the protoplasmic matrix of bone, is constantly being anabolized and catabolized at one and the same time; a factor which increases catabolism would lead to very much the same net result as a factor which inhibits anabolism, but there would be some differences; it is my belief that the “S” hormone [cortisol] is anti-anabolic rather than catabolic. . . . The anti-anabolism . . . is contrasted with the increased anabolism due to an excess of the “N” hormone [testosterone] in the adreno-genital syndrome. This anti-anabolism of protoplasm in Cushing’s syndrome accounts for not only the osteoporosis, but the muscular weakness, the thin skin, probably the easy bruisability, and possibly the atrophy of the lymphoid tissues and thymus.

Nonetheless, in the intervening years, the physical examination of patients suspected to have glucocorticoid excess focused on the anabolic changes, essentially to the exclusion of the antianabolic changes. With the rapid increase in the rate of obesity in the general population, Cushing’s syndrome can no longer be reliably separated from the metabolic syndrome of simple obesity on the basis of anabolic signs alone. However, the antianabolic changes in Cushing’s syndrome are very effective in making this distinction. This review focuses on the problems introduced into the diagnosis and differential diagnosis of Cushing’s syndrome by the obesity epidemic and on ways to alter the traditional approach, using the antianabolic changes of excess cortisol to separate patients with Cushing’s syndrome from obese patients with the insulin-resistant metabolic syndrome.

PHYSICAL EXAMINATION

Andreas Vesalius (1514–1564) published his transformational work on human anatomy, De Humani Corporis Fabrica Libri Septem, in 1543. It is the book that corrected many of Galen’s anatomical errors. The book was met with considerable hostility. As an example, Jacobus Sylvius (Jacques Dubois, 1478–1555), the world’s leading anatomist at the time and Vesalius’s former mentor, on being asked his opinion of the work, replied, “Galen is not wrong. It is man that has changed, and not for the better.”6 This was not true then, but it is true now.

Approximately one third of the U.S. population is obese. The worldwide prevalence of the metabolic syndrome among obese persons is conservatively estimated at 10%; that is, approximately 12 million people have the obesity-related metabolic syndrome.7,8 The clinical picture of this syndrome is almost the same as that of Cushing’s syndrome.9,10 The prevalence of undiagnosed Cushing’s syndrome is about 75 cases per 1 million population, or 24,000 affected persons. On the basis of these prevalence estimates, the chance that a person with obesity, hypertension, hirsutism, type 2 diabetes, and dyslipidemia has Cushing’s syndrome is about 1 in 500. In Harvey Cushing’s era, when obesity was rare, making the diagnosis of Cushing’s syndrome was the most certain aspect of the management of this disorder. Today, making the diagnosis is the least certain aspect in the care of patients with Cushing’s syndrome.

The metabolic syndrome caused by glucocorticoid hypersecretion can be differentiated from the obesity-associated metabolic syndrome with the use of a careful assessment of Albright’s antianabolic effects of cortisol. These effects — osteopenia, thin skin, and ecchymoses — are present in patients with Cushing’s syndrome but not in patients with simple obesity.

Patients in whom osteoporosis is diagnosed radiographically are more likely to have Cushing’s syndrome than those who do not have osteoporosis, with a positive likelihood ratio of 11.11-13 Today, a z score of −2 at the lumbar spine supports this criterion. Skinfold thickness is conveniently measured with an electrocardiographic caliper that has the points dulled with a sharpening stone and the screws tightened so that the gap is maintained when the caliper is removed from the skinfold. The skin over the proximal phalanx of the middle finger of the nondominant hand is commonly used for this measurement

(Figure 1FIGURE 1Measurement of Skinfold Thickness.). A thickness of less than 2 mm is considered to be thin skin. Patients who have thin skin are more likely to have Cushing’s syndrome, with a positive likelihood ratio of 116

(Figure 2FIGURE 2 Comparison of Skinfold Thickness in Patients with Cushing’s Syndrome and Those with Other Conditions Related to Insulin Resistance.).13-15 Finally, patients who have three or more ecchymoses that are larger than 1 cm in diameter and not associated with trauma such as venipuncture are more likely to have Cushing’s syndrome than are patients without such findings, with a positive likelihood ratio of 4.13,16

If we know the prevalence of undiagnosed Cushing’s syndrome in the population of persons with the obesity-related metabolic syndrome, we can begin to calculate the probability that a person has Cushing’s syndrome, using the likelihood ratios for the antianabolic features observed on physical examination. Likelihood ratios can be converted into probabilities with the use of Bayes’ theorem. This conversion is markedly facilitated by the Fagan nomogram for this purpose.17

The prevalence of undiagnosed Cushing’s syndrome is not known, but it can be estimated. Two persons per 1 million population die from adrenal cancer every year.18 The current life span for patients with adrenocortical carcinoma, after diagnosis, is between 2 and 4 years.19,20 Allowing 3 years to make the diagnosis, the prevalence of undiagnosed Cushing’s syndrome is 6 cases per million. In most case series of Cushing’s syndrome, an average of 8% of patients have adrenal carcinoma.21 If 6 per million is 8% of the group, the total Cushing’s syndrome group is 75 persons per million, or 24,000 persons. If all 24,000 patients are included in the metabolic syndrome group, comprising 12 million people, the prevalence of Cushing’s syndrome is 0.002, or 0.2%. With a probability of 0.2% and a likelihood ratio of 116 for thin skin, 18 for osteopenia, and 4 for ecchymoses, the probability that a patient with these three findings has Cushing’s syndrome is 95%.

URINARY FREE CORTISOL

The diagnosis of all endocrine diseases requires a clinical presentation that is compatible with the disease, as well as identification of the pathophysiological cause. An assessment for excess glucocorticoid effects can be made by measuring the 24-hour urinary free cortisol level.22 There are two kinds of free cortisol: plasma protein-unbound cortisol and cortisol unconjugated to sulfuric or hyaluronic acid. Protein-unbound cortisol is filtered in the glomerulus and then reabsorbed in the collecting system. About 3% of filtered cortisol ends up in the urine. This free cortisol in the urine is unconjugated. Thus, the urinary free cortisol level is a direct reflection of the free, bioactive cortisol level in plasma. The free cortisol level is quantified in a 24-hour urine sample by averaging the increased secretion of cortisol in the morning and the decreased secretion in the afternoon and at night. Urinary creatinine is also measured to determine whether the collection is complete. Creatinine levels of less than 1.5 g per day for men and less than 1 g per day for women indicate incomplete collection, and the test should be repeated in patients with these levels.

Unconjugated cortisol can be extracted directly from urine with a nonpolar lipid solvent. After extraction, the cortisol is purified by means of high-pressure liquid chromatography and then quantified with a binding assay, usually radioimmunoassay. Free cortisol also can be quantitated directly by means of mass spectroscopy. The urinary free cortisol assay of choice uses high-pressure liquid chromatographic separation followed by mass spectrometric quantitation.23 With the use of this assay, the urinary free cortisol level in healthy adults ranges from 8 to 51 μg per 24 hours (mean [±SD], 23±8). Clinical depression increases urinary free cortisol excretion, and most studies show that the level of urinary free cortisol ranges from 10 to 60 μg per day in patients with typical clinical signs and symptoms of depression. If we use 60 μg per day as the cutoff between normal values (<60 μg per day) and elevated values (≥60 μg per day), urinary free cortisol excretion of 62 μg per day or more has a positive likelihood ratio of 11.24 Thus, in a patient presenting with obesity, hypertension, type 2 diabetes, and hirsutism who has thin skin, osteopenia, ecchymoses, and an elevated urinary free cortisol level, the probability of Cushing’s syndrome is 1 (100%). For such patients, the clinician should move directly to a differential diagnostic evaluation.

DEXAMETHASONE-SUPPRESSION TEST

The dexamethasone-suppression test is commonly used in the diagnosis of Cushing’s syndrome. This test was developed by Grant Liddle in the early 1960s as a differential diagnostic test to separate corticotropin-dependent from corticotropin-independent Cushing’s syndrome. This is now done by measuring the plasma corticotropin level. Unfortunately, dexamethasone suppression has continued to be used as a screening test for Cushing’s syndrome.

The control group for this test comprises patients with obesity and depression in whom cortisol secretion is not suppressed in response to an oral dose of 1 mg of dexamethasone at midnight. Of the current U.S. population of 360 million people, approximately one third (120 million people) are obese. Of those who are obese, 10% (12 million people) have depression. In half these patients (6 million people), the plasma cortisol level will not be suppressed in response to a dexamethasone challenge. On the basis of my estimate of the current prevalence of undiagnosed Cushing’s syndrome (24,000 cases) and the estimate of the at-risk population (6 million persons), the positive predictive value of the dexamethasone-suppression test is only 0.4%. Thus, this test should not influence what the physician does next and should no longer be used for this purpose.

OUTLIERS

For patients with convincing evidence of Cushing’s syndrome on physical examination and an elevated 24-hour urinary free cortisol level, the differential diagnostic process outlined below should be initiated. However, a small group of patients will not meet these criteria.

Some patients have a strongly positive physical examination but low or zero urinary free cortisol excretion. Plasma corticotropin levels are suppressed in these patients. These patients are receiving exogenous glucocorticoids. The glucocorticoid must be identified, and a plan must be made for its discontinuation. Sometimes the glucocorticoid is being given by proxy (e.g., by a parent to a child), and no history of glucocorticoid administration can be found. Nevertheless, the glucocorticoid must be identified and discontinued.

Other patients have few or no clinical signs of Cushing’s syndrome but do have elevated urinary free cortisol excretion. Plasma corticotropin is measurable in these patients. They are usually identified during an evaluation for arterial hypertension. All such patients should undergo inferior petrosal sinus sampling to determine the source of corticotropin secretion. Ectopic sources are almost always neoplastic and are usually in the chest.25 Patients with eutopic secretion usually have the syndrome of generalized glucocorticoid resistance.26

Finally, a few patients have convincing findings on physical examination coupled with a normal urinary free cortisol level. In such cases, the clinician should make sure that urinary free cortisol is being measured with high-performance liquid chromatography and mass spectrometry, that renal function is normal, and that the collections are complete. “Periodic” Cushing’s syndrome must be ruled out by measuring urinary free cortisol frequently over the course of a month.27 If these efforts fail, the patient should be followed for a year, with urinary free cortisol measurements performed frequently. No additional tests should be performed until the situation is sorted out. More tests would be likely to lead to an unnecessary surgical procedure.

DIFFERENTIAL DIAGNOSIS

FIGURE 3Differential Diagnosis of Cushing’s Syndrome.. If plasma corticotropin is measurable, the disease process is corticotropin-dependent. If corticotropin is not measurable, the process is corticotropin-independent.

Corticotropin-dependent causes of Cushing’s syndrome are divided into those in which the corticotropin comes from the pituitary (eutopic causes) and those in which the corticotropin comes from elsewhere (ectopic causes). This differentiation is made with the measurement of corticotropin in inferior petrosal sinus plasma and the simultaneous measurement of corticotropin in peripheral (antecubital) plasma immediately after corticotropin-releasing hormone stimulation of pituitary corticotropin secretion. In samples obtained 4, 6, and 15 minutes after stimulation with corticotropin-releasing hormone, eutopic corticotropin secretion is associated with a ratio of the central-plasma corticotropin level to the peripheral-plasma corticotropin level of 3 or more. Ectopic corticotropin secretion is associated with a central-to-peripheral corticotropin ratio of less than 3. The positive predictive value of this test is 1 (Figure 4

Although some authorities suggest that inferior petrosal sinus sampling can safely be bypassed in patients with corticotropin-dependent Cushing’s syndrome and a well-defined pituitary adenoma, I disagree. The incidence of nonfunctioning pituitary microadenomas is between 15% and 40%.29 This means that up to 40% of patients with ectopic secretion of corticotropin have an incidental pituitary abnormality. If it is assumed that the pituitary abnormality is responsible for corticotropin secretion, 15 to 40% of patients with ectopic secretion of corticotropin will be misdiagnosed and submitted to a transsphenoidal exploration of the sella turcica and pituitary gland. The prevalence of ectopic corticotropin secretion in the population of patients with undiagnosed Cushing’s syndrome is about 10%, accounting for 2400 patients. Up to 40% of these patients, or 960, have an incidental pituitary tumor. The mortality associated with transsphenoidal microadenomectomy is 1%.30 If all 360 to 960 patients undergo this procedure, there will be up to 10 deaths from an operation that can have no benefit. For this reason alone, all patients with corticotropin-dependent Cushing’s syndrome should undergo inferior petrosal sinus sampling to confirm the source of corticotropin secretion before any surgical intervention is contemplated.

Patients with eutopic corticotropin secretion are almost certain to have a corticotropin-secreting pituitary microadenoma. An occasional patient will have alcohol-induced pseudo–Cushing’s syndrome. The slightest suggestion of alcoholism should lead to a 3-week abstinence period before any surgery is considered.31

Patients with ectopic corticotropin secretion are first evaluated with computed tomography (CT) or magnetic resonance imaging (MRI) of the chest. In two thirds of these patients, a tumor will be found.25 If nothing is found in the chest, MRI of the abdominal and pelvic organs is performed. If these additional imaging studies are also negative, there are two options: bilateral adrenalectomy or blockade of cortisol synthesis. If blockade is chosen, the patient should undergo repeat scanning at 6-month intervals.32 If no source is found by the end of the second year, it is unlikely that the source will ever be found, and bilateral adrenalectomy should be performed for definitive treatment (Doppman JL: personal communication).

Corticotropin-independent Cushing’s syndrome is usually caused by an adrenal neoplasm. Benign tumors tend to be small (<5 cm in diameter) and secrete a single hormone, cortisol. The contralateral adrenal gland is suppressed by the cortisol secreted from the tumorous gland. If the value for Hounsfield units is less than 10 and the washout of contrast material is greater than 60% at 15 minutes, the tumor is almost certainly benign.33 Such tumors can be treated successfully with laparoscopic adrenalectomy.

The syndromes of micronodular and macronodular adrenal dysplasia usually affect both adrenal glands. The nodules secrete cortisol. Corticotropin is suppressed, as is the internodular tissue of the adrenal glands. Percutaneous bilateral adrenalectomy, followed by glucocorticoid and mineralocorticoid treatment, is curative.

Adrenal tumors secreting more than one hormone (i.e., cortisol and androgen or estrogen) are almost always malignant. Surgical removal of all detectable disease is indicated, as is a careful search for metastases. If metastases are found, they should be removed. This usually requires an open adrenalectomy. It goes without saying that adrenal tumors, nodules, and metastases should be treated by the most experienced endocrine cancer surgeon available.

If the plasma cortisol level on the morning after a transsphenoidal microadenomectomy is 0, the operation was a success. The patient should be treated with oral hydrocortisone, at a dose of 12 mg per square meter of body-surface area once a day in the morning, and a tetracosactide (Cortrosyn) stimulation test should be performed at 3-month intervals. When the tetracosactide-stimulated plasma cortisol level is higher than 20 μg per deciliter (551 μmol per liter), cortisol administration can be stopped. The same rule applies in the case of a unilateral adrenalectomy. If the adrenalectomy is bilateral, cortisol, at a dose of 12 to 15 mg per square meter per day, and fludrocortisone (Florinef), at a dose of 100 μg per day, should be prescribed as lifelong therapy.

SUMMARY

The obesity epidemic has led to necessary changes in the evaluation and treatment of patients with Cushing’s syndrome. The most dramatic change is the emphasis on the antianabolic alterations in Cushing’s syndrome, which can provide a strong basis for separating patients with Cushing’s syndrome from the more numerous patients with obesity and the metabolic syndrome. More can be done along these lines. Likelihood ratios are known for proximal muscle weakness and can be known for brain atrophy and growth failure in children.

The dexamethasone-suppression test, although still very popular, no longer has a role in the evaluation and treatment of patients with Cushing’s syndrome. Only three biochemical tests are needed: urinary free cortisol, plasma corticotropin, and plasma cortisol measurements. Urinary free cortisol excretion is the test that confirms the clinical diagnosis of Cushing’s syndrome. To be trustworthy, it must be performed in the most stringent way, with the use of high-pressure liquid chromatography followed by mass spectrometric quantitation of cortisol. Measurement of plasma corticotropin is used to separate corticotropin-dependent from corticotropin-independent causes of Cushing’s syndrome and to separate eutopic from ectopic secretion of corticotropin. Inferior petrosal sinus sampling should be performed in all patients with corticotropin-dependent Cushing’s syndrome because of the high prevalence of nonfunctioning incidental pituitary adenomas among such patients. Measurement of plasma cortisol has only one use: determining the success or failure of transsphenoidal microadenomectomy or adrenalectomy. If the plasma cortisol level is not measurable on the morning after the operation (<5 μg per deciliter [138 μmol per liter]), the procedure was a success; if it is measurable, the operation failed. The surgeon must not administer intraoperative or postoperative synthetic glucocorticoids until the plasma cortisol level has been measured.

Successful evaluation of a patient who is suspected of having Cushing’s syndrome requires an endocrinologist who is skilled in physical diagnosis. Also required is a laboratory that measures urinary free cortisol using high-performance liquid chromatography and mass spectrometry and that can measure plasma cortisol and plasma corticotropin by means of radioimmunoassay.

Inferior petrosal sinus sampling is performed by an interventional radiologist. The treatment for all causes of Cushing’s syndrome, other than exogenous glucocorticoids, is surgical, and neurosurgeons, endocrine surgeons, and cancer surgeons are needed. This level of multidisciplinary medical expertise is usually found only at academic medical centers. Thus, most, if not all, patients with Cushing’s syndrome should be referred to such a center for treatment.

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No potential conflict of interest relevant to this article was reported.

SOURCE INFORMATION

From the Division of Endocrinology, Diabetes, and Clinical Nutrition, Oregon Health and Science University, Portland.